1. Field of the Invention
This invention relates generally to process control, and, more particularly, to a method and apparatus for presenting process control performance data.
2. Description of the Related Art
Statistical process control techniques are commonly used to monitor the operation of manufacturing processes, systems, or individual manufacturing tools. Commonly, various measurements related to the process being monitored are compiled and plotted on a control chart. The control chart has control limits, which, if violated, immediately indicate an error condition requiring investigation. Certain error conditions result from special causes, such as a defective tool, operator error, material defect, process changes, trends, etc., that may be corrected by process optimization or redesign.
Generally, the data gathered is evaluated against various rules to determine if an error condition has occurred. Although, various rules may be used, many companies have adopted the xe2x80x9cWestern Electric Rules,xe2x80x9d originally developed by the Western Electric Company. The rules specify that an error occurs if:
Rule 1: One measurement exceeds three standard deviations from the target (i.e., 1 greater than 3"sgr");
Rule 2: Two out of three consecutive measurements exceed two standard deviations from the target on one side of the target (i.e., ⅔ greater than "sgr");
Rule 3: Four out of Five consecutive measurements exceed one standard deviation from the target on one side of the target (i.e., ⅘ greater than "sgr"); and
Rule 4: Eight consecutive points on one side of the target.
Referring to FIG. 1, a graph of a typical control chart 10 is provided. The control chart may represent any number of measurements pertaining to a particular line, process, or tool, for example. On the x-axis 12, the measurement dates are recorded. The y-axis 14 represents the measurement values. The target for the process being measured is designated by a target line 16 (e.g., 175). Upper and lower control limits 18, 20 are also shown. In the control chart of FIG. 1, exceeding the control limits 18, 20, corresponds to a rule 1 violation, i.e., the measurement deviating from the target by more than three standard deviations. The data point 22 represents the eighth consecutive data point on the positive side of the target, resulting in a rule 4 violation.
In some applications, a particular line, process, or tool may be used with various operating parameters to accomplish different tasks. For example, a tool commonly used in the manufacture of semiconductor devices is a metal deposition tool. Semiconductor wafers are processed in the metal deposition tool using different parameters to control the formation of a metal layer. Typically, for each lot of wafers, measurements are taken of the thickness of the deposited metal to gauge the performance of the metal deposition tool. The individual lot measurements may be averaged to determine a single data point for inclusion on the control chart. Control charting is conducted on various measurable parameters. A particular metal deposition tool may use numerous recipes (i.e., sets of operating parameters), depending on the specific desired qualities of the metal layer being deposited. The particular recipe used by the metal deposition tool may be changed frequently.
Control charting the performance of the metal deposition tool using multiple recipes is burdensome, because the targets and control limits are different for each recipe. Accordingly, measurement data is independently charted for each recipe, yielding a large number of control charts. The problem with the large number of charts is exacerbated by the fact that in a manufacturing environment, such as a semiconductor fabrication facility, there are commonly multiple metal deposition tools being tracked and also multiple types of other tools being tracked. Collectively, the number of control charts that require updating and review can become resource intensive. In a typical semiconductor manufacturing facility, there can be as many as 13,000 individual control charts. This large number of control charts poses a resource problem. Due to the sheer number of control charts, many may only receive a cursory review and important information may be overlooked.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
One aspect of the present invention is seen in a method for presenting performance data from a process flow. The method includes providing a tool link associated with a first subset of the performance data for at least one tool in the process flow; providing a recipe link associated with a second subset of the performance data for at least one recipe in the process flow; displaying the first subset of the performance data in response to the tool link being selected; and displaying the second subset of the performance data in response to the recipe link being selected.